add ternary style to javascript.md

[kevinbarabash]

The preferred ternary style is the following:

• if it can fit on a single line, put it on a single line, e.g. const color = selected ? 'green' : 'orange'
• if it can't fit on a single line, put the ? and : at the start of each line, e.g.

const result = reallyVeryLengthConditional
    ? superLongComputationOfPositiveResult()
    : superLongComputationOfNegativeResult();

const style = selected
    ? {
        color: 'green',
        fontWeight: 'bold',
    }
    : {
        color: 'orange',
    }